Method for siliconizing carbon-containing materials

Abstract

A method for treating workpieces that consist of porous carbon material with liquid silicon with the formation of silicon carbide, comprising the steps: Preheating porous carbon workpieces under inert gas to the selected operating temperature T B 1, feeding liquid silicon to the porous carbon workpieces at an operating pressure p B 2 and an operating temperature T B 2, and impregnating the porous carbon workpieces with liquid silicon, reaction of the liquid silicon in the workpiece at a temperature T B 3 with the formation of silicon carbide that consists of carbon and silicon, gassing the workpiece with inert gas and cooling from the operating temperature T B 3 to the conditioning temperature T k , cooling the workpieces to room temperature, the temperature T B 3 being greater than or equal to the temperature T B 2, and the workpiece in step d of the method no longer being in contact with liquid silicon outside of the workpiece.

1. A method for treating workpieces which workpieces consist of porous carbon material with liquid silicon with the formation of silicon carbide, the method comprising the steps:
 a) preheating porous carbon workpieces under inert gas to the selected operating temperature T B 1, 
 b) feeding liquid silicon to the porous carbon workpieces at an operating pressure p B 2 and an operating temperature T B 2, and impregnating the porous carbon workpieces with liquid silicon, 
 c) reacting the liquid silicon in the workpiece at a temperature T B 3 with the formation of silicon carbide, 
 d) gassing the workpiece with inert gas and cooling from the operating temperature T B 3 to the conditioning temperature T k , and 
 e) cooling the workpieces to room temperature, 
 
       wherein the temperature T B 3 is greater than the temperature T B 2, and the workpiece in the step d is not in contact with liquid silicon outside of the workpiece. 
     
     
       2. The method according to  claim 1 , further comprising dropping to the operating pressure p B 1 of no more than 100 hPa, between steps a) and b). 
     
     
       3. The method according to  claim 1 , wherein the operating temperature T B 1 is between 1300° C. and 1800° C. 
     
     
       4. The method according to  claim 1 , wherein the operating temperature T B 2 is between 1450° C. and 1700° C. 
     
     
       5. The method according to  claim 1 , wherein the operating temperature T B 3 is between 1500° C. and 2000° C. 
     
     
       6. The method according to  claim 1 , wherein the operating temperature T B 3 is at least 50 K more than the operating temperature T B 2. 
     
     
       7. The method according to  claim 1 , wherein in step b), the silicon mass taken up by the workpiece is measured by weighing a basin before attachment of the workpiece and after infiltration and removal of the workpiece. 
     
     
       8. The method according to  claim 1 , wherein the workpiece comprises at least two fittings, having tapering sections and wherein the method further comprises separating the fittings from the workpiece. 
     
     
       9. The method according to  claim 1 , whereby the steps are performed in sequence. 
     
     
       10. A method of siliconizing a material comprising, in sequence:
 introducing a carbon-containing workpiece into a first chamber of a device, and flushing the first chamber with inert gas; 
 heating the workpiece to a first operating temperature; 
 opening a lock separating the first chamber from a second chamber; 
 moving the workpiece into a second chamber; 
 closing the lock; 
 bringing the workpiece to an operating pressure of less than about 1 Pa and a second operating temperature; 
 introducing liquid silicon, at a third temperature, into the workpiece, and permitting the silicon to penetrate into pores of the workpiece to form silicon carbide while preventing the workpiece from contacting liquid silicon outside the workpiece; and 
 subjecting the workpiece, in a third chamber, to an inert gas comprising cooling the workpiece to a conditioning temperature; wherein the second operating temperature is less than or equal to the third temperature. 
 
     
     
       11. The method of  claim 10 , further comprising reducing the pressure of the second chamber. 
     
     
       12. The method of  claim 11 , wherein the reducing step comprises reducing the pressure by 1 bar. 
     
     
       13. The method of  claim 10 , wherein the first temperature is from 1300° C. to 1800° C. 
     
     
       14. The method of  claim 10 , further comprising introducing a second workpiece into the first chamber after the moving step. 
     
     
       15. The method of  claim 10 , wherein the second operating temperature is from 1450° C. to 1700° C. 
     
     
       16. The method of  claim 10 , wherein the liquid silicon is delivered from a basin, and further comprising determining the amount of silicon taken by the workpiece by calculating a difference in mass of the basin following the introduction step.